Eicon Networks ISDN NT1 Especificações descarregar pdf (Página 53)

Protocol

A protocol describes a procedure.

When you declare your taxes, you complete a form. There will be boxes on this form where you state your

name, your income, deductions, etc. This makes it easier for the person (or machine) that has to process the

form; they will know exactly where to find each item of data.

There is also a set of rules which will describe what happens to the form inside the tax office. If you declare

income from another country, it's likely that your form will be sent to different department from those forms

where no such income has been declared.

Data communications are very similar. You use a protocol to communicate information to another person (or

computer). If you both follow different rules about how the information will be laid out, you won't be able to

understand each other. The communications protocol will also dictate the actions that must be performed

given the information received.

SNA

SNA stands for Systems Network Architecture.

This is a family of protocols defined by IBM over the last 30 years for use with their mainframes and mid-

range computers. There are also third party implementations (including Eicon Technology) of some of the

protocols on PCs. It is widely used in large organisations such as banks, public utilities and public

administration for creating large networks.

PPP

PPP stands for Point to Point Protocol.

This protocol is widely used for dial-up access to the Internet. All communications on the Internet are carried

by a family of protocols called the internet protocol suite. One of the features of PPP provides a mechanism

for reliably transporting the internet protocol suite across unreliable telephone lines.

PSTN or POTS

PSTN stands for Public Switched Telephone Network. POTS stands for Plain Old Telephone Service.

Both of these terms refer to the conventional analogue telephone system. Often these expressions are used

to make contrast with ISDN.

MLPPP

This stands for Multi-Link Point-to-Point Protocol.

This form of PPP is able to coordinate data across several parallel connections. It ensures that all items of

data have been properly assembled in the correct sequence at the receiving station before passing them

onward.

It is frequently used across two ISDN B channels, but can be used with any form of data communications,

such as modems; and across any number of data links.

When using MLPPP, it is advisable to use data links which are of approximately the same speed (eg. 2 B

channels; or 1 B channel and a 56K modem). If the data links have greatly different speeds, the data

throughput will be limited by the speed of the slowest link. This is because the receiving station will always

be waiting for data from the slowest link to complete some of the logical units of data, before they can be

passed onward.

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Eicon Networks ISDN NT1 Especificações Página 53